1. Field of the Invention
The present invention relates to an image processing apparatus executing recognition processing of characters or other data from image information received from a transmission line.
2. Description of the Related Art
Facsimile (hereinafter referred to as FAX) apparatuses have been spread widely as information terminals. Fax has been used in offices and shops as part of an information network to establish an order receiving and issuing process has been implemented using a FAX line between a terminal installed in a shop and a host computer.
The order receiving and issuing process is realized by receiving FAX image information such as an order issuing slip, etc., from a shop using a FAX apparatus installed in the host computer side and then recognizing character patterns in the FAX image information with a character recognizing apparatus (hereinafter referred to as optical character recognition, or OCR). The off-line type FAX-OCR system has been widely used. In the off-line type FAX-OCR system, the FAX image information received from a shop is output once to the receiving recording sheet in the host computer side and then the output receiving recording sheet is manually input to the OCR for the purpose of order receiving and issuing work.
However, with continuous progress in the versatility of the information network system and the rapid expansion in the amount of information to be processed, improvement in the processing rate of information is now required. Particularly, to attain high efficiency of order receiving and issuing work and reduction of personal cost, the existing off-line type FAX-OCR system is quickly being replaced by an on-line type FAX-OCR system. In the on-line type FAX-OCR system, the image information received by FAX is sent directly to the OCR for recognition, without passing through the receiving recording sheet.
In the image processing apparatus (hereinafter referred to as FAX-OCR apparatus) which generally recognizes character patterns in the image information received by FAX with OCR of the image information received by FAX applied by the FAX apparatus, if a code error is generated due to noise, etc. on the line while the image information is being received, the image information received by FAX may include a line error. Accordingly, a disturbance in the image obtained by encoding the image information received by FAX is generated.
FIG. 1 is a block diagram illustrating a FAX input controller 10 of the FAX-OCR apparatus of the related art. FIG. 2 is a diagram explaining disturbance in an image due to a line error. The receiving process of the FAX image input from the communication line will be explained with reference to FIGS. 1 and 2.
Referring now to FIG. 1, an analog signal carrying image data and communication sequence data is received by a network control unit (hereinafter referred to as NCU) 1 from a network control line (not shown in FIG. 1). After the analog signal is demodulated into a digital signal in the modulator/demodulator 2, an image data part of the digital signal is transmitted to an image information expanding unit 4 from a controller 3; the communication sequence data part other than the image data is used as a control signal for controlling the modulator/demodulator 2.
The digital image data includes the data obtained by encoding a continuous length (hereinafter referred to as run-length encoding) of black pixels or white pixels for every scanning line and the data obtained by adding, after the above-mentioned data, the end of line (hereinafter referred to as EOL) code indicating the end of each scanning line.
The controller 3 detects the EOL from the digital image data, transmits the image data to the image information expanding unit 4 in units of each scanning line and instructs the image information expanding unit 4 to begin the expanding process of data. The image information expanding unit 4, having received the instruction for the data expanding process, executes the expanding process on the image data in units of each scanning line.
For example, if the digital image data for one scanning line is assumed to be "01 11001110001110011", the image data can be divided (beginning with the left side of the foregoing digital sequence) into five code words of (1) "0111", (2) "0011", (3) "1000", (4) "11" and (5) "10011"; respective code words are encoded by the run-length encoding method to mean that (1) "continuous white pixels indicate 2", (2) "continuous black pixels indicate 5", (3) "continuous white pixels indicate 3", (4) "continuous black pixels indicate 2" and (5) "continuous white pixels indicate 8".
When this image data is expanded, image data consisting of 20 pixels as shown in FIG. 2(A) is obtained, and thus has the same length (L) as the scanning line when the expanding process is executed normally.
However, the second code word, "0011" in the digital image data may be "0010" due to an error caused by the line noise. If the erroneous second code word "0010" means that "continuous black pixels indicate 6" by the run-length encoding, when the foregoing image data (which includes the above-mentioned erroneous second code word) is expanded, an image consisting of 21 pixels is obtained, as shown in FIG. 2(B).
Therefore, since the length of the expanded image data does not match the length of the scanning line, an expansion error is detected by the expansion error detecting unit 5. The scanning line data, including the foregoing error, is therefore replaced with the preceding scanning line data. However, when this replacement is performed, the horizontal line disappears, resulting in an inaccurate representation of, and a disturbance of, the image.
Particularly when the above-mentioned image inaccurate representation is generated, in the character pattern or at an area near the character pattern which is the object of the character recognizing processing, erroneous recognition occurs since the expansion error detecting unit 5 detects for each scanning line whether image expansion has been performed normally or not.
If image expansion is not carried out correctly, the number of expansion errors is counted.
The comparing unit 7 determines whether the number of errors counted by the expansion error detecting unit 5 exceeds a threshold value preset in the threshold value setting unit 6 (for example, the number of scanning lines corresponding to two percent of the number of scanning lines of a page). If the number of errors counted by the expansion error detecting unit exceeds the threshold, the image is considered to have poor reproducibility which can easily generate erroneous recognition. In the foregoing event, the comparing unit 7 issues an instruction to disconnect forcibly the line to the NCU 1.
As explained above, a problem in the FAX-OCR apparatus of the related art is that the line is forcibly disconnected depending on whether the number of scanning lines generating an expansion error has exceeded the fixed threshold value, in order to reduce a drop in the character recognition efficiency due to line noise.
However, with the increasing versatility of information network systems, not all image information received is intended for character recognition. For example, a slip requiring character recognition and a general document which should be output as an image without character recognition are transmitted together in a single FAX transmission. Accordingly, character recognition is often not appropriate for the image information received.
A general document for which character recognition is not appropriate is one output as an image with reproducibility confirmed visually. For example, there may be no problem in visually verifying a general document, even if an expansion error is generated in the scanning lines corresponding to five (5) percent of the number of scanning lines of a page. However, in the FAX-OCR apparatus of the related art, if an expansion error is generated in the scanning lines corresponding to two or more percent of the scanning lines of a page, the line is disconnected forcibly, even when the image information received is a general document. Accordingly, the receiving process performance for the FAX image information is lowered, which presents a problem in the related art.
Meanwhile, if the line is not disconnected, even when the image information received is a slip or other item which is considered to be the object of character recognition, until the scanning lines generating the expansion error become five (5) percent of the scanning lines of a page, deterioration of the performance for the FAX image information receiving process may be avoided. However, the possibility of receiving the image having poor reproducibility increases. Accordingly, performance of the character recognition process for the FAX image information is lowered, which presents another problem in the related art.